Black-backed Woodpecker occupancy is extensive in green conifer forests of the southern Cascade Mountains, Oregon
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VOLUME 16, ISSUE 1, ARTICLE 4 Verschuyl, J., J. L. Stephens, A. J. Kroll, K. E. Halstead, and D. Rock. 2021. Black-backed Woodpecker occupancy is extensive in green conifer forests of the southern Cascade Mountains, Oregon. Avian Conservation and Ecology 16(1):4. https://doi.org/10.5751/ACE-01725-160104 Copyright © 2021 by the author(s). Published here under license by the Resilience Alliance. Research Paper Black-backed Woodpecker occupancy is extensive in green conifer forests of the southern Cascade Mountains, Oregon Jake Verschuyl 1, Jaime L. Stephens 2, Andrew J. Kroll 3, Katherine E. Halstead 2 and Dennis Rock 4 1 National Council for Air and Stream Improvement, 2Klamath Bird Observatory, 3Weyerhaeuser, 4Wildlife Investigations ABSTRACT. Black-backed Woodpeckers (Picoides arcticus) are widely considered a burned forest specialist across much of their range. Several recent studies have examined their occurrence in “green” coniferous forests that have not been recently burned, but Black- backed Woodpecker occupancy and factors influencing occupancy in these forest types remain largely unexamined. We worked on the east slope of the southern Oregon Cascade Mountains and used playback call surveys with repeated visits to 90 transects in 2014 and 2015 to estimate occupancy probabilities by forest type while controlling for detection probability. We detected Black-backed Woodpeckers on 86% of survey transects in green forests composed primarily of mixed conifer, lodgepole pine (Pinus contorta), or ponderosa pine (P. ponderosa). We examined associations between occupancy probability and structural covariates in unburned forests, and found that occupancy did not vary with annual precipitation, large snag density, or snag basal area. Modeled mean occupancy across all transects was 0.87 (95% CI: 0.78–0.93). Detection probability varied during each survey season, with transect-level detection probability reaching a maximum of 0.79 (95% CI: 0.70–0.85) in mid-June. Given high occupancy of green forests by Black-backed Woodpecker in our study area, we suggest that additional study of vital rates in green forests is critical for supporting conservation and management decisions for this species. Occurrence importante du Pic à dos noir dans les forêts de conifères verts du sud des montagnes Cascade, Oregon RÉSUMÉ. Le Pic à dos noir (Picoides arcticus) est reconnu comme un spécialiste des forêts brûlées dans une grande partie de son aire de répartition. Plusieurs études récentes ont examiné la présence de cette espèce dans des forêts de conifères « verts » (c.-à-d. qui n'ont pas brûlés récemment), mais son occurrence et les facteurs qui l'influencent dans ce type de forêts restent largement inexplorés. Nous avons travaillé sur le versant est des montagnes Cascade du sud de l'Oregon et avons utilisé des enregistrements et fait des visites répétées sur 90 transects en 2014 et 2015 pour estimer la probabilité d'occurrence par type de forêt, tout en ajustant pour la probabilité de détection. Nous avons détecté des Pics à dos noir sur 86 % des transects dans des forêts vertes composées principalement de conifères mixtes, de pins tordus (Pinus contorta) ou de pins ponderosa (P. ponderosa). Nous avons examiné les liens entre la probabilité d'occurrence et les covariables structurelles dans les forêts non brûlées, et avons constaté que l'occurrence ne variait pas en fonction des précipitations annuelles, de la densité de gros chicots ou de la superficie basale de chicots. L'occurrence moyenne modélisée sur l'ensemble des transects était de 0,87 (IC 95 % : 0,78-0,93). La probabilité de détection a varié au cours de chaque saison de relevé, atteignant un maximum de 0,79 (IC 95 % : 0,70-0,85) à la mi-juin à l'échelle du transect. Étant donné la forte présence du Pic à dos noir dans les forêts vertes de notre aire d'étude, nous pensons que des études sur les taux vitaux dans les forêts vertes devraient être effectuées pour éclairer la prise de décision touchant la conservation et la gestion de cette espèce. Key Words: Black-backed Woodpecker; fire; green forest; occupancy; Oregon Cascades; Picoides articus; playback calls INTRODUCTION addition to) fire-surrogate management treatments within fire- Woodpeckers (family Picidae) are often considered keystone prone landscapes (Hanson and North 2008, Hutto 2008, Cahall species because they produce cavities in hard live and dead trees and Hayes 2009, Dudley et al. 2012). that are subsequently used by many other secondary cavity- Individual Black-backed Woodpeckers often colonize burned nesting species (Aubrey and Raley 2002, Remm and Lõhmus areas soon after fire when availability of key prey resources such 2011). Woodpecker species are often used to guide forest as larvae of wood borers (Coleoptera: Cerambycidae and management decisions due to their link to overall bird community Buprestidae) and bark beetles (Coleoptera: Curculionidae) is health (Mikusinski et al. 2001, Drever et al. 2008) and to the highest. High woodpecker densities have been found in the 4- to disproportionate influence they have on the communities in which 6-year period postfire (Saab et al. 2007, Nappi and Drapeau 2009, they occur (Martin et al. 2004, Virkkala 2006). Due to their Saracco et al. 2011), with density often declining 6-10 years common use of recently burned forests in western North America, postfire (Siegel et al. 2016). Because habitat colonization is Black-backed Woodpeckers (Picoides arcticus) are often used to attributed largely to natal dispersal (Tremblay et al. 2015a, Seigel support the maintenance of high-intensity fires instead of (or in Address of Correspondent: Jake Verschuyl, PO Box 1259, Anacortes, WA , USA, 98221, jverschuyl@ncasi.org
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et al. 2016), and adults exhibit breeding-site fidelity (Tremblay et METHODS
al. 2015a), reductions in Black-backed Woodpecker density over
time may reflect the lifespan of individuals that colonize an area Study area
shortly postfire. Our study area included the Chemult, Chiloquin, and Klamath
Relative to recently burned areas, Black-backed Woodpecker Ranger Districts of Fremont-Winema National Forest in the
density and habitat associations outside recently burned areas southern Cascade Mountains of Oregon, USA (Fig. 1). Elevation
have received less attention in western North America. In boreal averaged 1575 m (range: 1300–2120 m) and spanned a gradient
forests of Alberta (Canada) and the northern Rocky Mountains of coniferous forest types that grow the on the volcanic soils of
(U.S.), Black-backed Woodpecker occupancy rates are the southern Oregon Cascades and upper Klamath Basin.
substantially greater in burned than in unburned forest (Hoyt and Dominant tree species in the study area include ponderosa pine,
Hannon 2002, Hutto 2008). However, in eastern boreal forests, lodgepole pine (Pinus contorta), and white fir (Abies concolor).
Black-backed Woodpeckers commonly use unburned black Precipitation during breeding seasons (April–July) varied from
spruce (Picea mariana) forests (Tremblay et al. 2009, 2010, 2015b), 71 mm (2014) to 84 mm (2015) (SNOTEL weather station, Sun
and in the Black Hills of South Dakota, they are found in Pass, Oregon, 1636 m elevation). Temperatures during that same
ponderosa pine (Pinus ponderosa) (Mohren et al. 2014, 2016). period averaged 12°C in 2014 and 13°C in 2015. Daily minimum/
Home ranges in unburned forest types include both open and maximum temperatures ranged from -7°C to 33°C, respectively.
forested areas (Tremblay et al. 2009), but foraging is generally The historical fire regime likely included frequent, low-intensity
restricted to older stands with recently dead snags (Tremblay et burns (Agee 1994). At the time surveys were conducted, only two
al. 2010). In eastern Canada, nesting Black-backed Woodpeckers transects were within 10 km of a recently burned forest (i.e.,
prefer stands with high densities of recently decayed snags wildfire occurring after the year 2000) (Fig. 1). Forest
(Tremblay et al. 2015b), and use recently harvested stands for management in the Chemult, Chiloquin, and Klamath Ranger
when suitable snags are available (Craig et al. 2019). Districts of Fremont-Winema National Forest includes dry forest
restoration to reduce fuel loads, improve wildlife habitat, and
Until recently, use of green, unburned forests by Black-backed maintain existing late-successional and old-growth forests. Active
Woodpeckers in the western portion of their range was assumed management includes thinning to remove smaller diameter
to be a result of spillover from burned areas and was generally subdominant or understory trees (17.8–53.3 cm diameter at breast
considered inconsequential to population viability (Odion and height [dbh]) while promoting old or large ponderosa pine stands
Hanson 2013). However, a survey across several National Forests (Charnley et al. 2017).
in California (Fogg et al. 2014) reported higher densities of Black-
backed Woodpeckers in green forests than were previously found
in burned forests of the northern Rocky Mountains, which Fig. 1. Study area and location of Black-backed Woodpecker
highlighted the potential importance of this forest type in (BBWO) survey transects, 2014–2015, southern Cascades,
supporting regional populations. Despite large fires in western Oregon, USA (NF: National Forest).
forests in recent years, most of the forest area within the range of
Black-backed Woodpeckers in western North America has not
burned recently enough to be considered optimal habitat (Hutto
2008, Odion and Hanson 2013, Hanson and Odion 2016).
If proposed genetic differences between populations in boreal
forests, the Black Hills, and Oregon/California (Pierson et al.
2010) define subspecies, it may become even more important to
understand how all forest types in a particular region support
viability of regional Black-backed Woodpecker populations.
Further, there is concern about the viability of the Oregon/
California population (Odion and Hanson 2013) due to potential
negative effects of fire suppression and postfire salvage logging
(Hanson and North 2008, Odion and Hanson 2013, Hanson and
Odion 2016). Robust estimates of Black-backed Woodpecker
occupancy of green forests is an important step in determining
the extent to which these forests provide habitat for this species.
Thus, there is a need to assess whether green forests, that have not
recently burned, provide habitat for Black-backed Woodpeckers,
especially in the westernmost portion of their range. Toward that
goal, we (1) estimated detection and occupancy probabilities of
Black-backed Woodpeckers in green forests along the east slope
of the southern Cascade Mountains, Oregon, and (2) evaluated
associations between occupancy probability and green forest
structural characteristics.
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Black-backed Woodpecker surveys random points. We collected tree data on variable radius survey
We selected a stratified random sample of 90 transects to plots based on a basal area factor of 40 (Criterion RD 1000
encompass the range of coniferous forest types present on electronic basal area factor scope/dendrometer). For each tree
National Forest lands within the study area. We used transects as within the plot, surveyors recorded species, dbh (cm), tree height
our sampling unit to maintain sampling efficiency and to ensure (m), and tree defect (e.g., presence of mistletoe, cavity, broken
that a significant portion of a Black-backed Woodpecker’s top). Within a 16-m radius plot, snags ≥ 3 m tall and dbh ≥ 10 cm
potential home range was surveyed. We overlaid a 500 x 500 m were recorded along with species, dbh, height, categorical decay
grid on the study area and randomly selected grid cell centroids class (Cline et al. 1980), and tree defect. Understory data were
as the northwest corner of a survey transect. Each transect collected to assess whether shrubs may indicate prey availability,
consisted of 15 survey points spaced 250 m apart and arranged as has been demonstrated for other species (Martinuzzi et al.
in a 3 x 5 point grid, which resulted in approximately 141 ha 2009). We measured shrub species and percent cover in 5%
sampled. It was not possible to define discrete forest stands based increments.
on common management history due to a long history of
overlapping and unquantified forest management treatments Statistical analyses
(thinning, etc.) that have been implemented across broad spatial The transect (n = 90) was the unit of analysis for determining
extents within the Fremont-Winema National Forest. Still, Black-backed Woodpecker occupancy and assessing relationships
individual transects were sited to remain within relatively with associated forest structure covariates, the latter derived from
homogenous forest types that lacked variation in seral stage or averaging eight vegetation plots per transect. The study employed
species composition. Adjacent transects were no closer than 1500 transect-scale analyses because individual survey points do not
m from one another and thus were considered spatially represent independent samples when using active playback calling
independent based on known home range sizes in green forests methodology. Individual woodpeckers are known to follow
(Tremblay et al. 2009). playback calls from station to station (Hartwig et al. 2002). Our
15-point transects were designed to sample an area equivalent to
Substantial differences in detection probability for Black-backed a relatively small Black-backed Woodpecker home range
Woodpeckers exist between point count and broadcast acoustical (Tremblay et al. 2009). We considered the sampled area of the
monitoring or playback-based surveys (up to four times as many transect to represent a forest stand and serve as the unit of analysis.
detections using playback calls), possibly due to the species’
relatively large home range size (Russell et al. 2009, Saracco et al. We used a model developed by MacKenzie et al. (2002) to estimate
2011) and generally cryptic behavior, except when responding to probability of occupancy of a forest stand by any Black-backed
territory disputes. Thus, we implemented playback call surveys Woodpecker. We conducted analyses in the package unmarked in
for Black-backed Woodpeckers following standard methodology R (R Development Core Team 2010, Fiske and Chandler 2011).
(Saracco et al. 2011). Surveys were conducted mid-April through Our expectation was that detection probability would peak during
July, which spanned the potential breeding season in the region. the sampling season (which closely followed the breeding season),
Each transect was surveyed three times per year, with different so we included a quadratic ordinal date covariate in the detection
transects surveyed each year. Surveys were limited to mornings portion of the model. Given the observational study design and
when rain, fog, or wind did not interfere with sight or sound. our general interest in evaluating associations between abiotic and
Surveys began within 10 minutes of local sunrise and were biotic covariates and occupancy, we fit individual models with
completed by noon. The survey protocol, developed by the only one covariate in the occupancy portion of the model (four
Institute for Bird Populations, was 6 minutes long, and consisted models total). We investigated effects of snag basal area (Rota et
of three increments of 30-second broadcasts followed by 1.5 al. 2014b), number of large snags (> 27 cm dbh) (Rota et al. 2014b),
minutes of listening each. This protocol has become the standard elevation (Fogg et al. 2014), and precipitation (Fogg et al. 2014),
for Black-backed Woodpecker monitoring in burned and which have all been shown to influence Black-backed Woodpecker
unburned forests of the Sierra Nevada (Fogg et al. 2014, Siegel et occupancy. We plotted the mean and standard deviation for
al. 2014). Surveyors played recordings using a Wildlife several vegetation characteristics (shrub species richness, shrub
Technologies model MA-15 caller at a standard volume (~90dB cover, tree density, tree dbh, snag basal area, and number of large
at 1 m). The caller was placed on a stump or log above the ground snags) to make comparisons between unoccupied sites, single
when possible, positioned parallel to the ground topography, and occupancy, and pair occupancy.
turned approximately 120° before each subsequent broadcast. To
minimize disturbance to nesting birds, we discontinued playback RESULTS
at the survey point after a Black-backed Woodpecker was Across two years of sampling, we detected Black-backed
detected. Woodpeckers on 77/90 (86%) transects. We detected single birds
and pairs on 41 (46%) and 36 (40%) transects, respectively; we did
Vegetation sampling not detect any Black-backed Woodpeckers on the remaining 13
We made detailed measurements of forest conditions around (14%) transects. We detected Black-backed Woodpeckers during
detection and nondetection locations to quantify habitat features 964/4050 individual surveys (24%). Most transects were in mixed
presumed to be of greatest importance to Black-backed conifer—true fir (Abies spp.)/pine (20; 22%), lodgepole pine (27;
Woodpeckers in the region (Cahall and Hayes 2009, Fogg et al. 30%), and ponderosa pine (20; 22%) forest types; we surveyed
2014). We completed vegetation surveys at eight points on each only a small number of transects in true fir (12; 13%) and
survey transect: up to four points where Black-backed Englemann spruce (Picea englemannii)/western hemlock (Tsuga
Woodpeckers were detected and the remainder at predetermined heterophylla) (4; 4%) forest types.
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Mean occupancy across all transects was 0.87 (95% CI: 0.78–0.93). Detection probability varied during the survey season, with
We did not fit occupancy models for forest type due to a lack of transect-level detection probability reaching a maximum of 0.79
variation in naïve occupancy for stands in mixed conifer (0.81), (95% CI: 0.70–0.85) in the middle of June (Fig. 4). However, we
lodgepole pine (1.00), and ponderosa pine (0.90), or because of note that only 38/270 (14%) of surveys were conducted before 1
small sample sizes in true fir (0.50) and spruce/hemlock (1.00). We June across both years. Therefore, uncertainty in detection
found little variation in occupancy by annual precipitation, large probability may reflect small sample sizes rather than actual
snag density, or snag basal area (Fig. 2). Black-backed Woodpecker variation in Black-backed Woodpecker responses prior to 1 June.
occupancy was not clearly related to elevation, although a positive Juvenile Black-backed Woodpeckers and active nest cavities were
association existed across our relatively narrow elevation gradient noted incidentally during playback call surveys in the latter part
(Fig. 2). We further explored forest structural characteristics based of the survey period.
on whether naïve occupancy status of transects was unoccupied
or occupied by singles or pairs. Transects with observed pair Fig. 4. Detection probability (95% CI) as a function of date for
occupancy had fewer than half as many trees on average (1.93 Black-backed Woodpeckers using green forest types, 2014–2015,
± 1.21 trees per basal area factor 40 plot) when compared to southern Cascades, Oregon, USA.
transects without detections (4.52 ± 1.67 trees per basal area factor
40 plot). There were approximately 24% fewer shrub species on
transects with observed pair occupancy (4.22 ± 0.89 shrub species)
when compared to transects without detections (5.55 ± 1.13 shrub
species). Transects with pair occupancy had an approximately 25%
smaller average tree dbh (34.65 ± 12.94 cm) when compared to
transects without detections (46.66 ± 8.29 cm). Finally, number of
snags/hectare was not different among transects with observations
of pairs or singles, and those lacking detections (Fig. 3).
Fig. 2. Association between occupancy (95% CI) and four forest
structure covariates for Black-backed Woodpeckers, 2014–2015,
southern Cascades, Oregon, USA.
DISCUSSION
Our study adds to a small but growing body of literature that has
documented Black-backed Woodpecker occupancy and nesting in
green forests (Fogg et al. 2014, Tremblay et al. 2015a), despite the
species’ well-documented association with burned forests across
its range (Hanson and North 2008, Hutto 2008, Cahall and Hayes
2009, Dudley et al. 2012). Mean transect-scale Black-backed
Woodpecker occupancy was 0.87 in green forests that were
composed primarily of mixed conifer, lodgepole pine, or
ponderosa pine, but also less commonly included true fir and
spruce/hemlock forests. The lack of substantial variation in
occupancy by annual precipitation, large snag density, or snag
Fig. 3. Summary of habitat covariates for Black-backed basal area may be due in part to low variation in occupancy across
Woodpeckers, 2014–2015, southern Cascades, Oregon, USA transects. Our results demonstrate consistently high Black-backed
(dbh: diameter at breast height). Woodpecker occupancy in green forests along the east slope of the
southern Cascade Mountains, Oregon, USA, and emphasize the
need for more inclusive treatment of how different forest types
contribute to population viability of this species in western North
America.
Transect-level occupancy in this study was much higher than
expected based on prior efforts. The mean occupancy estimate of
0.87 on 90 transects (141 ha of surveyed area each) suggests that
Black-backed Woodpecker density is likely higher along the east
slope of the southern Oregon Cascades than in the Sierra Nevada
where Fogg et al. (2014) reported a density of 0.21 birds/100 ha in
green forests. In that same geographic area, Saracco et al. (2011)
found mean occupancy to be 0.097 and a detection probability of
0.772 in burned forests. Regional population estimates thatAvian Conservation and Ecology 16(1): 4
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consider Black-backed Woodpecker use of green forests may be trees and high snag density (Fogg et al. 2014). Black-backed
substantially higher than would be expected from burned forests Woodpecker occupancy was consistently high across the relatively
alone. modest elevational gradient of our study area, which created a
challenge for linking occupancy to forest structure or abiotic
Despite comparable detection probabilities, it should be noted
attributes. Although an analysis undertaken for individual survey
that some variation in occupancy estimates across studies is likely
points may have provided greater variation in occupancy status
the result of different survey methods. Many prior assessments
when compared to transect-scale results, relationships between
of Black-backed Woodpecker occupancy and habitat associations
occupancy forest structure would likely be spurious because
have used passive point count sampling (Haggard and Gaines
individuals were drawn toward the playback call from significant
2001, Smucker et al. 2005) or a mix of point count and playback
distances. Black-backed Woodpeckers were commonly seen
methodology (Saracco et al. 2011), often using passive surveys
following the observer between multiple points (more than two)
and playback surveys occurring in sequence as separate visits
within a transect. Responses to playback calls were often first
(Fogg et al. 2014). We applied playback call methodology
heard > 200 m from the observer but were noted to be moving
(Saracco et al. 2011) on three separate visits spread across the
closer, eventually (within the same survey period) within 25 m of
breeding season (instead of sequential sampling) to estimate
the survey point.
Black-backed Woodpecker occupancy at transect scales. Using
transect-level data in the analysis addresses potential bias that Availability of food resources has been directly linked to
might result from incorrectly associating occupancy with forest population regulation (Villard and Benninger 1993, Murphy and
structural characteristics at an individual survey point when birds Lehnhausen 1998, Rota et al. 2014a) and is undoubtedly an
may have traveled in response to the playback call. However, we important component of Black-backed Woodpecker occupancy
suggest that future studies consider study designs that use patterns in both burned and unburned forests. High-severity fires
individual Black-backed Woodpecker territories as the unit of create relatively high initial prey availability and are reported to
inference, as doing so will allow for the identification of forest be particularly important for Black-backed Woodpeckers
structural characteristics in green forests associated with (Smucker et al. 2005, Hanson and North 2008, Hutto 2008),
occupancy, and measures of fitness such as reproduction and whereas other disturbance types such as widespread beetle
survival. Since passive sampling during a point count visit has infestations do not provide the same magnitude of resource
four times lower detection rates than playback calls (Russell et al. (Bonnot et al. 2008, 2009, Tingley et al. 2020). Tremblay et al.
2009, Saracco et al. 2011), and playback methodology maintains (2016) found that both male and female Black-backed
a potential bias in observations of occupied habitat, we propose woodpeckers had higher food delivery rates and spent less time
using autonomous recording units as an alternative method for at the nest per delivery in burned forests compared to green forests,
surveying territories more effectively. which suggests that greater effort may be needed to raise young
in green forests. Forests in our study area did not have recent fire
Although our study did not examine colonization or persistence,
or beetle damage, and we assumed they would have fewer prey
we did find evidence of nesting and fledglings, which indicated
resources, which would lead to lower occupancy. Lower tree
that breeding occurred on a portion of the transects. In green
densities on transects where pairs were observed (Fig. 3) is in
forests, Fogg et al. (2014) found site colonization and local
contrast to prior findings that higher tree densities were indicative
extinction probabilities to be low (0.05 and 0.19, respectively),
of greater Black-backed Woodpecker occupancy in green forests
which indicated the relative stability of those home ranges. Even
(Hoyt and Hannon 2002) and postburn (Hutto 2008). This may
within burned forests, complex dynamics can influence postfire
indicate the importance of biophysical factors (e.g., volcanic soils,
colonization and persistence (Stillman et al. 2019). Tingley et al.
areas of early frost) that may be regulating tree vigor and health,
(2018) found colonization and persistence declined across and
and ultimately forage availability. A previous study further east
within burned areas with time since fire, and at a given fire site,
on the Fremont-Winema National Forest did not detect any
colonization decreased with fire size and increased with fire
Black-backed Woodpecker nests in unburned forests, compared
severity and later ignition dates.
to 21 nests in nearby burned areas (Russell et al. 2009). In an
Black-backed Woodpecker associations with forest structural experimental study in the same region, Kroll et al. (2010, 2012)
characteristics and abiotic factors have been well described in found Black-backed Woodpeckers breeding successfully in forests
some regions (northern Rocky Mountains [Smucker et al. 2005, with bark beetle infestations and infested forests that were salvage
Dudley and Saab 2007, Dudley et al. 2012], Black Hills of South logged. A pilot demography study implemented in 2016 in our
Dakota [Bonnot et al. 2008, 2009, Rota et al. 2014b, 2015], eastern study area found active nests on 23% of previously surveyed
boreal forests of Quebec [Huot and Ibarzabal 2006, Tremblay et transects, which provided evidence that Black-backed
al. 2009, 2010, 2015a, Nappi et al. 2010], mixed conifer forests in Woodpeckers hold territories and nest in green forests (Halstead
California [Saracco et al. 2011, Seavy et al. 2012, Fogg et al. 2014]). and Stephens 2015).
Tremblay et al. (2009) found Black-backed Woodpeckers
Further study of key vital rates that underlie populations and are
successfully bred in unburned forest with 35 m3/ha of dead wood,
linked to recruitment (e.g., nest survival, postfledgling survival)
of which 42% (15 m3/ha) was represented by dead wood in the
will be necessary to determine the full extent to which green forests
early decay stage. In green forests of the Sierra Nevada,
support Black-backed Woodpeckers on a regional basis. In
California, Black-backed Woodpecker occupancy was better
eastern Canadian boreal forest, it has been reported that
explained by physiographic variables rather than forest structure,
unburned habitat may provide Black-backed Woodpeckers with
where the strongest relationships were with elevation, latitude,
more temporally stable resources, which has potential benefit to
and forest type (lodgepole pine), but to a lesser extent, with large
long-term persistence of the species (Tremblay et al. 2015a). IfAvian Conservation and Ecology 16(1): 4
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the same line of reasoning applies to forests of western North Forest Ecology and Management 257:1119-1128. https://doi.
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Woodpecker populations on landscape and regional scales,
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particularly with the variable temporal and spatial pattern of
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CONCLUSION
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(Fogg et al. 2014), eastern Canada (Tremblay et al. 2009, 2015a), characteristics and dynamics in Douglas-fir forests, western
the Black Hills of South Dakota (Mohren et al. 2014, 2016), and Oregon. Journal of Wildlife Management 44:773-786. https://doi.
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backed Woodpeckers were found using green forests. Collectively, Craig, C., M. J. Mazerolle, P. D. Taylor, J. A. Tremblay, and M.-
these studies establish that this species exhibits different habitat A. Villard. 2019. Predictors of habitat use and nesting success for
associations across its range and, at least in some areas, uses green two sympatric species of boreal woodpeckers in an unburned,
forests extensively. A critical next step is to quantify vital rates in managed forest landscape. Forest Ecology and Management
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contribution of these two forest types in supporting populations,
and to document the extent to which individuals breeding in these Drever, M. C., K. E. H. Aitken, A. R. Norris, and K. Martin.
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Responses to this article can be read online at: Dudley, J. G., and V. A. Saab. 2007. Home range size of Black-
backed Woodpeckers in burned forests of southwestern Idaho.
https://www.ace-eco.org/issues/responses.php/1725
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Dudley, J. G., V. A. Saab, and J. P. Hollenbeck. 2012. Foraging-
Acknowledgments: habitat selection of Black-backed Woodpeckers in forest burns of
We thank Chris Adlam, Jaime Blankenship, Patrick Flaherty, Eva southwestern Idaho. Condor 114:348-357. https://doi.org/10.1525/
Leach, Kendall Norcott, Andrew Orahoske, Graeme Riggins, and cond.2012.110020
Andrew Wiegardt for field support. Additional logistic support was Fiske, I., and R. Chandler. 2011. Unmarked: an R package for
provided by Kelley Breen, Katie Knox, Frank Lospalluto, Suzanne fitting hierarchical models of wildlife occurrence and abundance.
Rock, Sarah Rockwell, and Heidi Timms. We appreciate the support Journal of Statistical Software 43:1-23. https://doi.org/10.18637/
and guidance from John Alexander for Klamath Bird Observatory's jss.v043.i10
scientific studies. Funding was provided by the National Council for
Air and Stream Improvement and the Bureau of Land Management. Fogg, A. M., L. J. Roberts, and R. D. Burnett. 2014. Occurrence
Jim Rivers provided thoughtful review of the draft manuscript. patterns of Black-backed Woodpeckers in green forest of the
Sierra Nevada mountains, California, USA. Avian Conservation
and Ecology 9(2):3. https://doi.org/10.5751/ACE-00671-090203
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